We might not be the best people to ask, because we actually avoid those kind of events.
Specifically because our f/os are all either in-system or in our partner system it’s weird and uncomfortable for us to have people writing to us ‘as’ them. It’s the same reason we’re reeeeeally overly picky with what x reader fic we read.
Likewise we wouldn’t feel like we knew enough about someone else’s f/o and their relationship to write a letter to them as their f/o.
There was one exception to that where 😼🔪 was sending messages to someone whose f/o was one of his kintypes but that… ended sadly.
Anyway, I know that didn’t really answer your question, sorry ^^;;
I guess the answer is we feel the same but for a different reason!